Laser direct writing of flexible multifunctional airflow sensors on the Kevlar fabric

The growing interest in flexible devices has emerged as a global trend due to their advantages in flexibility, lightweight structure, and wearability, addressing the limitations of traditional devices. While wearable airflow sensors have been previously reported, the development of flexible fabric-based airflow sensors capable of functioning in environments with open flames-critical for fire rescue operations-has yet to be explored, largely due to the poor fire resistance of conventional fabrics. In this work, we first present a flexible, wearable, multifunctional airflow sensor with excellent fire-resistant properties, fabricated through a simple direct laser writing process. This sensor maintains airflow detection capabilities even in the presence of open flames. Typically, the fabrication of fabric-based sensors involves complex procedures such as carbon materials doping or vapor-phase deposition, leading to lengthy preparation cycles and high costs. Furthermore, fabric-based devices are inherently prone to flammability. To address these challenges, we introduce twice-vertical laser-induced graphene (TVLIG) as a sensitive and reliable component for fire-resistant airflow sensors. The resulting TVLIG/Kevlar fabric can be integrated into various garments, particularly protective suits, to form sensitive, fire-resistant airflow sensors capable of detecting airflow velocity and direction in both two-dimensional (2D) and three-dimensional (3D) spaces during fire incidents. Additionally, the TVLIG patterns can be expanded to multifunctional platforms, such as glucose detection for injured individuals, offering further applications in rescue operations. This functional expansion reduces the burden on rescue personnel and streamlines device preparation. With its outstanding sensing capabilities, fire resistance, and expandability, the developed flexible airflow sensors show great potential for various real-world rescue scenarios, promising advancements in wearable sensing technology for rescue engineering.